Frequency and phase correction in oscillators



Feb. w, 1948. M. MORRISON FREQUENCY AND PHASE CORRECTION IN OSCILLATOBS Filed Sept. 23, 1945 2 SheetsSheet l CLASSA AMPL/F/EP PHASE SH/FTER I N VEN TOR.

Feb. 10, 1948. M. MORRISOVN 2,435,751

FREQUENCY AND PHASE CORRECTION IN OSCILLATORS Filed Sept. 23, 1943 2 Sheets-Sheet 2 IN VEN TOR Fi .2 I

Patented Feb. 10,1948

"umreo OFFICE FBEQUEN r AND rnaseeomncrion IN (IS CILLATORS "Montford Morrison!-Upper Mohtclair,Q 3.

Application September 23,1943, SeriaI=No 503,568

,flhe present invention relates to electrical cir- ,ci'iits comprising elements employed-for sync-bro" nizing one electronic oscillator with another .source of alternatingcurrent, and has particular relation tocircuits employing a stabilized source or local oscillations to be'kept in s'yn'ch'ronism witna remotely disposed source of alternations,

, and more particularly when the remote source is not continuously available locally for synchronizing purposes, as for instance in certain types of synchronous telegraph circuits.

Among the objects of the invention are; toproyide a'more definite phase instant of introducing energy into certain types of self-excited oscillating circuits; to provide a more definite phase instant of introducing energy into certain types of oscillating circuits when excited from external sources and to provide more accurate phase and frequency "correction for self-excited oscillators.

In certain types of telegraphic signaling, a local order-to preserveitsshape suflicient'ly, in order .toserve its purpose well at the receiving end.

In the present invention a lowfrequency sine wave is transmitted for synchronization purposes Source of stabilized oscillations is required in the receiving terminal equipment and this local osdilator 'is required to operate not only in synbhr'onism with av source of alternating current in the transmittin terminal equipment'but the two sources: of alternating, and in some cases otherwise periodic, current, must be maintained with 'a high'de'g'ree oi constancy in a predetermined relative phase position between the two.

.In the prior art, simple sine waves have been used as a means of synchronizing one source of alternating current with an oscillator, 'butthis method has the disadvantage of lack of definiteiijess with respect to the exact phase position at which the synchronization takes place. In-all prior art cases'the point of synchronization employed is during a rising part of the voltage wave and in the case of the sine wave the steepness or this rising voltage i diiferent for difie'rent, parts or 'thew'a've as Well as it is difierentfor different amplitudes of voltage values, which resultsin fie,

distinctly indefinite position of synchronization. LTD overcome this lack of definitejne'sfsjin the point of synchronization. attempts. have been l'liiide 'in'the p ior art to yflChroniZe te1 5g-raph terminal equipment by meansloi impulses which are really, in 'efiect, forms of lobes ,of sinewa es of a considerably higher frequenc than the cycles synchronized and While this 'so-called impulse synchronization. has certain advantages over-the lower frequency sine wave method of synchronization, other 'diiiiculties are met with in its employment. It i much more diiiicult to transnut ever communication circuits and requires fa ni h quality or transmission characteristic in $1 frequencies.

Further and other features and objects will be pointed out and .obviousupon reading the followingde'scription in connection with the drawings, in which Fig. l is' a simplified diagrammatic circui't embodying the present invention and Fig. 2 is a series -of graphs useful in understanding its operation.

Referring to Fig. 1, the circuit circumscribed by the dotted area I is a relaxation circuit employing a low-pass filter instead of the conventional resistancestructure, the circuit contained in the area circumscribed by 2 is a high Q closed oscillating .circuit,"the output of which is fed into a class Ai amplifier 3, the output of which said amp'li'fier is fed through phase-shifter 4, the output of which is fed through a circuit circumscribed by dotted line .5, which comprises a full wave rec- 'tifier, the output of which is delivered to the grid circuit of a gaseous triode 6, through a parallelied coupling transformer, as is well understood in the art. The grid circuit of gaseous triode 6, is

provided with aconventional bias battery 1 and a current limiting resistor 8. Gaseous triode 6 serves as the triggertube for the relaxation circuit i throughthe closed oscillating circuit 2 and the reactor 9.

, Thepurpose oi the low-pass filter in circuit I is vto limii'. .the peak value of the plate current in I gaseous-triode 6 and at the same time provide a higher electrical efliciency in the-relaxation cir- -.cait. :The reactor 9 assistsin extinguishing the "dischargein thegaseous triode 6.

i .=Relaxation circuit 1, together with the closed oscillating-cir'c'uit 2 and its'oth'er related circuits,

is als'e subject to operation by a gaseous triode ecnnec'ted'mpareuel with gaseous triodet. and having an exactly similar input grid circuit with the exception or the source of alternating current'utiliz'e d in the 'grid circuit which is derived from generator "I l With reference to'the operation of the present invention, it will be convenient to assume that 05- .cillat'or Z'Iis in operatioh and generating a-Sine value. -'re'present the form of plate current in gaseous It will be appreciated by those skilled in the" art that the output voltage form circuit is purely alternating, the zero position automati- 'cally assumed being such that if the areas of the positive and negative lobes of the wave be integrated mathematically, this operation will equate the positive and negative current flowing during a complete cycle. In other words, the

voltage across the output terminals of circuit 5, as

read on a dArsonval volt meter, will always be zero.

This output voltage of circuit Sibeing biased by battery I, is caused to assume the position with reference to the zero line shown along abscissa 13, by curve l2, Fig. 2.

With such a curve as illustrated by I2 the bias of gaseous triode 6 is always greater than that required for break-down with the maximum plate voltage employed, except at the cusps I3. These cusps are very sharp and occur, of course, at the zero instants of the alternating current wave.

By the addition of a half-wave rectified curj rent such as shown at I4, abscissa B, Fig. 2, every other cusp may be removed if and when desired, though this addition is unnecessary in the pres- 'ent embodiment. 4

Referring to Fig. l, the phase shifter 4 is adjusted such that the cusps l3, abscissa B, Fig. 2,

are properly timed in order to trigger the relaxation circuit I, which supplies the impulse energy to the closed oscillator 2, the illustrated.

circuits functioning as a self-excited electronic oscillator, as hereinbefore described.

The voltage across the output of the relaxation circuit I, follows the general form shown along abscissa C, Fig. 2, and when the gaseous triode 6 is triggered by one of the cusps l3, this voltage drops off very rapidly, as shown at l5, abscissa C, and in such a manner that no subsequent triggering by the parallel connected gaseous triode It) will have any eifect upon the relaxation circuit until the voltage has risen to substantially its normal value shown at l6. In this way it is obvious that the relaxation circuit is triggered by whichever gaseous triode operates to trigger it first, and only after the relaxation voltage has risen substantiallyto its maximum The impulses along abscissa D, Fig. 2,

triode t. The duration of these impulses may -be adjusted to any'predetermined value, though the shorter the period of the impulse the more -nearly the oscillator circuit 2 follows its natural period of oscillation, for as long as the oscillator circuit is under power absorption it tends to follow a forced form of oscillation, whereas durthat of the source H, Fig. 1. the cusps of the two waves in the grid circuits of the two gaseous triodes l0 and 6 may be represented by the curves along abscissa E, Fig. 2, in which I! represents the grid circuit voltage of triode 6 and I8 represents the grid circuit voltage of triode l0.

It will be appreciated if the source of altervnating current H is of a highlystandardiz'ed :order and that the frequency of oscillator 2 is slightly less than that of generator n and such that the frequency of oscillator 2 will at no time be faster than that of generator ll, oscillator 2 may be expected to run for considerable periods of time self-oscillated without drifting away greatly from its standardized frequency and if and when generator II is thrown into the circuit because of sequence of events illustrated along abscissa E, Fig. 2, oscillator Z WillDIOlllDtly be brought into exact frequency of and t8 exact phase position with generator Hbecause of gaseous triode 8 losing control of the relaxation circuit due to being behind that in phase of gaseous triode Hi, as has been pointed out. i It will be appreciated that oscillator 2 may drift considerably out of phase and even as much as shown along abscissa F, Fig 2, without the standardized frequency generator being unable to correct the frequency in phaseposition of oscillator 2. I L

It will be appreciated by those skilled in the art that in the present embodiment, the practical application of this invention to the many uses to which it may be put has been omitted for the sake of clearness in teaching the spirit of the invention, and those skilled in the various arts to which the invention appertains will appreciate the obvious applications thereto. I

The scope of the invention is set forth in the claims hereunder.

What I claim is:

1. In a, relaxation oscillator of alternating cur rents having power currents initiated by. electrical breakdown in gaseous discharge tubes; a relaxation generator of oscillations including a source of power, a feed-back circuit supplying control current to maintain said oscillations and a gaseous discharge tube receiving control current from said feed-back circuit to initiate power currents; a second gaseous discharge tube connected in parallel with first said tube to also initiate power currents in said oscillator, and an independent source of control current for second said tubes;

2. In a relaxation oscillator of alternating currents having power currents initiated by electrical breakdown in gaseous discharge tubes; a re- I laxation generator of oscillations including ,;a

source of power, a feed-back circuit supplying control current to maintain said oscillations and a gaseous discharge tube receiving controlcuifrent from said feed-back circuit to initiate power currents; a second gaseous discharge tube con} nected in parallel with first said tube to also initiate power currents in said oscillator, an independent source of control current for second said tube, and electrical circuit means to cause one and back circuit supplying control current to maintain said oscillations and a gaseous discharge tube receiving control current from said feed-back circuit to initiate power currents; a second gaseous discharge tube connected in parallel with first said tube to also initiate power currents in said oscillator, an independent source of alternating control current for second said tube having independent timing, and electrical circuit means to cause one and only one of said tubes to initiate power currents in said oscillator during any one oscillation period, whereby the timing of the power currents generated is fixed by the one tube initiating said currents.

4. In a relaxation oscillator of alternating currents having power currents initiated by electrical breakdown in gaseous discharge tubes; a relaxation generator of Oscillations having inherent timing and a source of power, a feed-back circuit supplying control current to maintain said oscillations and a gaseous discharge tube receiv ing control current from said feed-back circuit to initiate powercurrents; a second gaseous discharge tube connected in parallel with first said tube to also initiate power currents in said oscil lator, an independent source of alternating control current for second said tube having predetermined timing, and electrical circuit means to cause the second said tube to initiate power currents in said oscillator when said inherent timing is different from said predetermined timing.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,153,179 Fitch Apr. 4, 1939 2,157,799 Norrman May 9, 1939 2,292,100 Bliss Aug. 4, 1942 2,215,776 Barnard Sept. 24, 1940 2,304,813 Gibbs Dec. 15, 1942 2,374,495 Morrison Apr. 24, 1945 

